The aim of RC repair is to restore the anatomical location and mechanical performance of the RC sufficiently to withstand the loading associated with functional activity.11) However, besides restoring its mechanical stability, enabling RC tendon healing under ideal conditions, to re-establish its biomechanical properties, plays an important role in successful RC repair.12) Therefore, we postulated that preserving the remnant RC tissue in a transtendinous RC tear would be better than sacrificing the tissue for the following reasons.
First, preserving the remnant tissue may help maintain proprioception of the RC. Joint structures are innervated by mechanically sensitive receptors termed mechanoreceptors that relay information to the central nervous system regarding movement, position, and forces exerted on shoulder structures.6,13−17) In the shoulder joint, there are mechanoreceptors in the coracoacromial ligament, RC tendons, musculotendinous junctions of the RC, and joint capsule.14) It is reasonable to speculate that RC tears are associated with structural and functional alterations of proprioceptors.16–21) Reduced or inconsistent proprioceptive information from the injured muscle–tendon unit and altered muscle reflex activity may impair shoulder proprioception and contribute to impaired kinematics and muscle recruitment. Consequently, the preserved remnant tissue on the footprint may help maintain as many mechanoreceptors as possible.
Second, the blood flow within the RC would also be preserved. The posterior humeral circumflex artery is the main vessel supplying blood to the supra- and infraspinatus tendons.22) Because the posterior humeral circumflex artery provides blood to the RC flowing from the humeral attachment toward the proximal RC, the remnant within the footprint has high vascularity in a transtendinous RC tear.23) As a result, the RC blood supply would inevitably be compromised if the remnant tissue were sacrificed.
Third, the natural enthesis of RC is maintained. The normal anatomy of the RC has four zones, from tendon to fibrocartilage to calcified fibrocartilage to bone. The ultimate goal of surgical repair is to replicate as much of this native enthesis as possible.24) Su et al. reported that enthesis-preserving RC repair gave better histological and biomechanical results than enthesis-removal RC repair in a rabbit model.25) By preserving the footprint remnant tissue, the RC can be repaired effectively with its native enthesis preserved within the RC.
Considering these advantages, we recommend a remnant-preserving tendon-to-tendon repair for transtendinous RC tears. If there is concern about the tissue quality of the lateral tendon segment or over-tension of the medial tendon segment, a suture anchor can be added for a more secure repair and to prevent retraction when necessary. Using this technique, anatomical repair of transtendinous RC tears can be achieved without excessive tension, and a biomechanical condition that promotes satisfactory tendon healing is established owing to the preserved remnant tissue.